In general, an organic electroluminescence (EL) device is composed of an anode, a cathode and one or more organic thin film layers placed between the anode and the cathode. When voltage is applied across the electrodes, electrons and holes are injected into the light emitting region from the cathode side and from the anode side, respectively. The injected electrons and holes recombine in the light emitting region and are promoted to an excited state, and light is emitted when the excited state returns to the ground state.
Because a wide variety of colors can be obtained when various luminescent materials are used for the light emitting layer, intensive studies on the practical use of an organic EL device, for example use in a display, are conducted. In particular, the studies on luminescent materials for the three primary colors, red, green and blue, are most extensively conducted, and the materials are studied intensively for the improvement of the properties.
As materials for such an organic EL device, phosphine oxide compounds are disclosed in PTLs 1 to 3. However, in the field of organic EL devices, development of new materials is required to further improve the performance of the devices.